TMS and the Neurology of Pain
Basic findings
The main interest of rTMS is to provide a noninvasive tool to study the efficacy and the role of the motor cortex or other cortical areas in the modulation of pain perception (Oxford Handbook). In 1995 Migita et al. showed that chronic neuropathic pain could be transiently relieved by the repeated application of a single pulse of TMS at low frequency (<0.3Hz) over the motor cortex. This research was followed by Lefaucheur et al. (1998) producing more significant and reliable analgesic effects by applying rTMS trains at 10 Hz over the motor cortex in patients with chronic neuropathic pain.
Ongoing research
Monitoring The Disease
Previous findings suggest that ventral lateral and medial prefrontal circuits may comprise an important part of a circuit of perceived controllability regarding pain (Borckardt et al., Pain, 2011).
Modulating The Disease
The motor cortex is the most widely used cortical target for TMS in the management of neuropathic pain (Borckardt et al., Clinical Journal of Pain, 2011). A meta analysis published in 2009 (Leung et al.) found a significant overall analgesic effect was detected with greater reduction in the pain visual analog scale with rTMS in comparison to sham. The trigeminal nerve or ganglion pain subgroup was found to have the greatest analgesic effect, followed by post-stroke supraspinal related pain, spinal cord, nerve root and peripheral nerve pain. In addition, multiple sessions and lower (>1 and ≤10 Hz) treatment frequency range (vs >10 Hz) appears to generate better analgesic outcome. The meta analysis summarised that rTMS appears to be more effective in suppressing centrally than peripherally originated neuropathic pain states.
The analgesic effects resulting from a single session of rTMS are too short-lived and thereby incompatible with durable control of chronic pain. Repeated sessions of rTMS on consecutive days are able to produce cumulative effects (Khedr et al. 2005). Additionally rTMS can be used as a predictive tool to select patients who will respond well to the surgical implantation of a cortical stimulator (Lefaucheur et al. 2004).
Links
References
- Borckardt et al., Clinical Journal of Pain, 2011.
- Khedr et al., Journal of Neurology, Neurosurgery and Psychiatry, 2005.
- Lefaucheur et al., Neurophysiologie Clinique, 2004.
- Leung et al., The Journal of Pain, 2009.
- Migita et al., Neurosurgery, 1995.
- The Oxford Handbook of Transcranial Stimulation.
